Single-carrier transmission is adopted in the existing CDMA2000 1xEvolution-Data Optimized (1xEV-DO) technology. In a 1xEV-DO system, an Access Terminal (AT) only uses one reverse carrier link to transmit information.
A higher data transmission rate is required for the development of data services. The Third Generation Partnership Project 2 (3GPP2) has proposed a new air interface evolution plan. In the first phase of the plan, a great increase in air interface data rate is enabled through Multiple Carrier EV-DO (NxEV-DO). It is required that the forward data rate is no lower than N×3.1 Mbps and the reverse data rate is no lower than N×1.8 Mbps, in which N is the number of carriers used by an Access Network (AN) or the AT. Further, it is required that the forward and reverse carriers be assigned dynamically and independently through the cooperation of the AN and the AT. The number of forward carriers and the number of reverse carriers are not required to be symmetric.
In an NxEV-DO system, an AT should be able to request an AN for the number of reverse carrier links the AT can support according to the AT's current power amplification state or other factors, and also be able to drop one or more reverse carrier links according to its power amplification state or other factors and report this to the AN.
FIG. 1 is a diagram illustrating the structure of a 1xEV-DO system, where the direction of a forward carrier link is defined from the AN to the AT and the direction of a reverse carrier link is defined from the AT to the AN. The components of the 1xEV-DO system are respectively described as follows:
Access Network (AN) is a network equipment configured to provide data connectivity between a packet switched data network (typically the Internet) and the ATs, and the AN is equivalent to a base station in a CDMA2000 system.
A packet Control Function unit (PCF unit) mainly provides between a wireless link and a wire link functions such as mapping, call control, mobility management, session management, data buffering and forwarding, and accounting information collection.
A packet Data Serving Node (PDSN) mainly provides functions such as link management, mobility management, address distribution, accounting information collection, data routing and tunnel encapsulation, and also supports the function of foreign agency for Mobile IP.
An accounting, Authentication, Authorization server (AAA server) mainly provides functions such as identity authentication and address distribution.
A mobile Switching Center (MSC) is a circuit domain voice switching center through which the circuit domain voice service is introduced.
In the existing 1xEV-DO system, when performing a configuration negotiation or establishing a traffic channel, the AT needs to establish a connection. There are mainly the following situations:
The AT initiates a connection request on its own initiative;
The AN sends a paging message, and the AT initiates a connection request when receiving the paging message;
The AT initiates a connection request when an initial establishment of a session or a configuration negotiation is required.
As shown in FIG. 2, the message flow in the case that the AT initiates a connection request on its own initiative includes the following processes.
S01: The AT sends a Connection Request.
S02: The AT sends a Route Update message to indicate the wireless circumstance.
S03: The AN sends a Media Access Control (MAC) layer Acknowledgement message to confirm that the Route Update message is received.
S04: The AN sends a Traffic Channel Assignment message.
S05: The AT establishes a Reverse Traffic Channel (RTC) and sends a pilot signal and a Data Rate Control (DRC) signal.
S06: The AN sends an RTC ACK message to confirm that the RTC is received.
S07: The AT sends a Traffic Channel Complete message on the reverse traffic channel.
S08: The AT starts to exchange data with the AN.
It can be seen from the prior art:
The AT is unable to request the AN for a reverse carrier link;
The AN does not know the number of reverse carrier links desired by the AT;
Only one reverse carrier link can be assigned to the AT, and the peak rate of the reverse carrier link is just 1.8 Mbps;
The forward and reverse data rates can not meet the requirement of the future service.